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I've heard that the Pentium III chip's processor serial number can compromise my privacy. How do I disable the PSN on my Pentium III system?

Sean Callen, Kingston, Ontario

Intel's PSN is a unique identifier that theoretically allows Web sites to pinpoint your surfing habits. PSN never became the supercookie many people feared: The critics' hue and cry held PSN in check.

So what's your computer's PSN status? If it isn't a Pentium III, you don't have a PSN. If you do have a PIII, your PSN is probably turned off already, per recommendations Intel made to PC vendors because of the controversy over privacy.

You can turn your PSN on or off via the hardware setup screen, but the method differs from one PC to another. On most PIII-based systems, you get to this screen by holding down Insert or Delete at the beginning of the boot-up process. Search the options to find the PSN off switch.

An Intel program tells you whether your PSN is turned on, and turns it off or on for you as you specify. Download it at Intel's support page. If PSN is disabled in your BIOS settings, you can't enable the feature using Intel's program. Instead, you'll get a message stating that 'the processor serial number has been disabled by another user, an application, or by your computer's hardware setup'.

When PSN is enabled in the BIOS, you can use Intel's PSN program to toggle between enabling and disabling your PSN. You're warned that 'enabling the processor serial number may allow this information to be read by Web sites'. After you click OK, a dialog box shows your PSN. If you click Settings and disable the feature, the dialog box indicates that the PSN is unavailable.

Once you turn the PSN off, can a program or Web site secretly turn it back on? Much controversy surrounds this question. Doing so would involve rebooting the CPU surreptitiously--no easy trick.

But even if some hacker managed to turn on your PSN for the fun of it, all he or she would get is a number. The PSN's true potential as a spying tool was checkmated as a result of the controversy, since the number is almost universally turned off. Intel says it will not put serial numbers in its Pentium 4 processors.